Ren 5 - Electrolyte Disorders Flashcards
What is the substance that is the precursor for vitamin D3 when combined with UV rays in the skin?
It is 7-Dehydrocholesterol.
What is another name for Vitamin D3?
Cholecalciferol.
What enzyme converts Cholecalciferol into 25-Hydroxycholecalciferol and where is it located?
It is 25-hydroxylase. It is found in the liver.
Which enzyme converts 25-hydroxycholecalciferol into 1,25-dihydroxycholecalciferol?
1alpha-hydroxylase that resides in the kidney.
Which hormone influences the enzyme 1alpha-hydroxylase?
Parathyroid hormone (PTH).
What is another name for 1,25-Dihydroxycholecalciferol?
Calcitriol, or 1,25-DHCC.
What does PTH do in the kidneys?
- Influence the enzyme that is in 1alpha-hydroxylase. 2. Stimulates the kidneys to increase the reabsorption of calcium and decrease reabsorption of phosphate.
What are some hormones that influence the kidneys?
- PTH. 2. Renin-angiotensin-aldosterone. 3. Atrial natriuretic peptide (ANP). 4. Vasopressin.
How does Atrial natriuretic peptide (ANP) influences the kidneys?
When the atria has increased volume load and increased atrial pressure, it send a signal to the kidneys to constrict the efferent arterioles and dilate the afferent arterioles, increasing GFR and leading to diuresis.
What happens to the serum in patients with SIADH?
Too much ADH causes too much reabsorption of water and concentrating too much the urine. Low serum osmolality and low serum sodium.
What are the causes of SIADH?
- Ectopic ADH production: small cell lung cancer. 2. Pulmonary pathology. 3. Head trauma. 4. Stroke. 5. CNS infections. 6. Drugs, especially cyclophosphamide. 7. Idiopathic.
What happens in diabetes insipidus?
- Increase in urine volume. 2. Urine is very dilute. 3. Serum osmolarity is high. 4. Decrease in urine specific gravity.
What happens in Central diabetes insipidus?
There is deficient or absent production of ADH from the pituitary.
What happens in nephrogenic diabetes insipidus?
Kidneys are unresponsive to ADH.
How does lithium cause nephrogenic diabetes insipidus?
It interferes with aquaporin being deposited in the lumen side of the principal cells.
What are substances that can cause nephrogenic diabetes?
- Lithium. 2. Demeclocycline. 3. Hypercalcemia. 4. Hereditary mutation of ADH receptor.
How are urine and serum osmolarity in Diabetes insipidus?
Decrease in urine osmolarity. Increase in serum osmolarity.
What is a water deprivation test and what does it check for? What would be a normal test result?
It checks for diabetes insipidus. In normal patients it causes a rise in urine osmolarity. In patients with DI, it will decrease urine osmolarity because they lack ADH to concentrate their urine.
How can we check if a patient’s diabetes insipidus is central against nephrogenic?
Do the desmopressin challenge: Give patient desmopressin. If the patient has central DI, it increases urine osmolarity because it corrected the problem of small/absent ADH (desmopressin is an analogue of ADH). If it doesn’t, then it is nephrogenic, failing to change to urine osmolarity.
What is the treatment for Central diabetes insipidus?
Intranasal desmopressin.
What is the treatment for nephrogenic Diabetes insipidus?
Hydrochlorothiazide: we use this diuretic to make the patient a little dehydrated so that the proximal tubule can collect more water so by the time it gets to the collecting tubule, it is a little more concentrated. Indomethacin: can be used with Hydrochlorothiazides, it inhibits the prostaglandin synthesis, reducing renal blood flow, and decreasing urine output, somewhat.
What is the treatment for lithium induced nephrogenic diabetes and how?
Amiloride blocks the sodium channels that lithium uses to enter the principal cell.
What can hyponatremia cause?
- Altered mental status. 2. Seizures. 3. Stupor. 4. Coma.
What does hypercalcemia cause?
[Stones, bones, abdominal groans, and psychiatric overtones]
-Confusion and delirium.
What does hypocalcemia cause?
Tetany. Trousseau sign. Chvostek sign. (cheek sign).
What does hypomagnesemia cause?
Tetany. EKG abnormalities: Wide QRS complex and Torsades de Pointes. Arrhythmia.
What does hypermagnesemia cause?
Depress the reflexes.
What does Hypokalemia cause?
Prolong the QT interval. V tach and Torsades. T waves: flattened. U waves.
What does hyperkalemia cause?
V tach. T waves: tall and peaked.
What happens to the T waves in hypokalemia versus hyperkalemia?
-T waves are tall and peaked in hyperkalemia. In HYPOkalemia, they are flattened.
How is the potassium in the serum compared to potassium intracellularly?
Potassium in the serum is low compared to the potassium inside the cells.
What kinds of things cause a shift of potassium out of the cells, causing hyperkalemia?
Low insulin. Beta-blockers. Acidosis. Digoxin. Cell lysis (i.e. Leukemia). Potassium-sparing diuretics. ACE inhibitors.
What kinds of things cause a shift of potassium into the cells, causing hypokalemia?
Insulin. Beta agonists. Alkalosis. Cell creation/proliferation (cancer). Loop diuretics. Thiazides.
What is a way to shift acutely potassium into the cell?
Beta agonsits like albuterol (nebulized). Alkalosis (IV bicarbonate). IV insulin (but give IV dextrose first).
What electrolyte disturbance causes pontine myelinosis if corrected too rapidly?
Hyponatrimia.
What electrolyte disturbance causes peaked T waves?
Hyperkalemia.
What electrolyte disturbance causes tetany?
Hypocalcemia.
What electrolyte disturbance causes arrhythmias?
Hyperkalemia. Hypokalemia. Hypomagnesium.
What electrolyte disturbance causes decreased deep tendon reflexes?
Hypermagenesia (Drip magnesium is used to fight uterine contractions in partum).
What electrolyte disturbance causes flattened T waves and U waves on EKG?
Hypokalemia.
What are diagnostic features of diabetes insipidus?
Polyuria. Dilute urine: low specific gravity, and low urine osmolarity. In water deprivation test, the urine osmolarity does not rise.
RFF: Treatment for central DI.
Desmopressin.
RFF: Treatment for nephrogenic DI.
HCTZ, Indomethacin, Amiloride.
RFF: Treatment for lithium-induced nephrogenic DI.
Amiloride.
What are the causes of Hypernatremia?
[The 6Ds] Diuretics. Dehydration. Diabetes insipidus. Docs (iatrogenic). Diarrhea. Diseas of the kidney.
